Had the teaser video not leaked early, it would have been a pretty sweet surprise — but we're willing to bet fans of Fall Out Boy and Paramore are still pretty pumped this morning ... because the two iconic acts are going on tour together this summer.

The co-headlining trek — aptly dubbed Monumentour — is set to kick off June 19 in Hartford, Connecticut, and will make stops in 30 cities across North America before coming to a close on August 17 in Concord, California. Pre-sale tickets go on sale Wednesday, January 15, with general presales to most shows beginning on January 17 through LiveNation.com.

The tour was accidentally announced Wednesday night, when a video featuring FOB and Paramore (minus proud new papa Jeremy Davis, who was represented in cardboard cut-out form) began making the rounds ... much to the consternation of Paramore frontwoman Hayley Williams, who, in her frustrations, invoked the name of Beyoncé.

Dang, girl. Despite being two of the genre's biggest acts, up until now, FOB and Paramore have never toured together ... no matter how desperately their fanbases demanded it. And though both acts have been established for a decade (or longer), this certainly doesn't seem like a nostalgia tour: Both bands are coming off rather remarkable 2013s, in which they each released successful comeback albums, scored hit singles, and launched large-scale arena tours.